The adverb 势必 emphasizes that if some action or phenomenon continues in a certain way, a certain result is inevitable.
势必 is placed before a verb (used as a predicate) in the second part of a complex sentence.
Scheme
action
势必
result
Pay attention
An action is stated in the first part of a sentence, and an inevitable result is stated in the second part.
Examples
他如果不准时回家,势必倒霉
If he doesn’t get home on time, it will be not good for him
tā rúguǒ bù zhǔnshí huí jiā, shìbì dǎoméi
如果他继续这样下去,势必有一天要蹲监狱
If he keeps this up, he is bound to go to prison one day